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NOTHING IN THE SKY SURPRISED an astronomer more than the sudden apparition of a new star where none had been seen before. When the legendary Tycho Brahe of Denmark glanced skyward one night and beheld such a sight, he declared it “the greatest wonder that has ever shown itself in the whole of nature since the beginning of the world.” De nova stella, Tycho’s eyewitness account of the 1572 marvel, argued that Aristotle had been wrong to call the heavens immutable. Surely the abrupt appearance of the new star and its subsequent disappearance a year later proved that change could occur in the realm beyond the Moon.
Not long after Tycho died in 1601, another nova burst into splendor. Both Galileo in Padua and Johannes Kepler in Prague observed the brilliant new star of 1604, which was so bright as to be visible in the daytime for more than three weeks. Although no comparable naked-eye nova ever materialized over the following centuries, a few fortunate astronomers who happened to be pointing their telescopes to the right place at the right time discovered seven more novae between 1670 and 1892. Then Mina Fleming found one. On October 26, 1893, while hunched over her light lectern with a magnifying glass during a routine perusal of a photographic plate newly arrived from Peru, she seized on a star with the peculiar spectrum unique to a nova—a dozen prominent hydrogen lines, all of them bright.
The director cabled the exciting news to Solon Bailey, who had taken the photograph more than three months earlier, on July 10. Pickering hoped new pictures by Bailey would disclose what, if anything, remained of the nova. Meanwhile Mrs. Fleming looked back in time through the plates to see what had preceded it, but found no trace in prior photographs of the same region. The star must have been dim indeed before its leap from obscurity to seventh magnitude.
The nova lay in a constellation defined and named in the mid-eighteenth century by Nicolas Louis de Lacaille, a French astronomer, on a voyage south. Where others might have seen beasts or deities, Lacaille perceived instruments of modern science, from Microscopium and Telescopium to Antlia (air pump) and Norma (originally Norma et Regula, for the surveyor’s square and rule). Now, thanks to Mrs. Fleming, the small, inconspicuous Norma gained fame as the home of the first nova to be detected by spectral photography. It was only the tenth such star to have been observed in recorded history, and it was hers.
Nova Normae’s most recent predecessor, the new star of 1891, had been espied visually through the telescope of an Edinburgh amateur, who alerted the Scottish astronomer royal by anonymous postcard. The timely aviso allowed observatories in Oxford and Potsdam to photograph the nova within days of its discovery. Now Pickering placed a picture of that nova’s spectrum next to Nova Normae’s. The two were virtually identical. Together, they made the ideal illustration for the announcement of the new discovery “by Mrs. M. Fleming,” which Pickering submitted in early November to Astronomy and Astro-Physics. “The similarity of these two new stars is interesting,” he pointed out in his article, “because if confirmed by other new stars it will indicate that they belong to a distinct class resembling each other in composition or physical condition.” Even more important, their similarity had enabled Mrs. Fleming to make the discovery, and might lead her to others as she continued sifting through the spectra collected for the Henry Draper Memorial.
Pickering regarded the nova—any nova—as the ultimate variable star. Novae figured first among the five types of variables he defined. Just as astronomers had divided the multitudes of stars into color or brightness or spectral categories in the ongoing effort to comprehend their nature, so, too, the rarer variable stars could be grouped by their behavior. A nova, a “new” or “temporary star,” flared and faded just once in a lifetime. Its brief glory thus distinguished Type I from the “long-period” variables of Type II, which underwent the slow, cyclical changes of one or two years’ duration, monitored by Pickering’s volunteer amateur corps. Type III experienced only slight changes, not easily followed via small telescopes; Type IV varied continuously in short time spans; and Type V revealed themselves to be “eclipsing binaries,” or pairs of stars that periodically blocked each other’s light.
One could only wonder at the cause of a nova’s rapid rise to brightness. Something—a stellar collision, perhaps?—made the star release and ignite enormous quantities of hydrogen gas. The spectra of the two recent novae presented perfect portraits of incandescent hydrogen. Had Pickering become aware of the outburst sooner, instead of fifteen weeks after the fact, he might have tracked Nova Normae through its slow decline, watching the bright lines fade to dark, and the spectrum resume the semblance of a normal star.
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SOLON BAILEY SUFFERED NO REMORSE at not having noticed Nova Normae himself. He had been entrusted with the day-to-day operation of the Arequipa station, the nightly rounds of photography, and the timely transfer of photographic plates to Harvard. Although he looked at every image to make sure it passed muster, the detailed scrutiny fell, as always, to the Cambridge staff of assistants and computers. He gladly added his voice to the chorus of congratulatory wishes now surrounding Mrs. Fleming.
Since Bailey’s return to Arequipa in late February 1893, he had grown enamored of the great globular clusters of stars visible in the pristine southern skies. These objects, each a mere fuzz patch or hazy star to the unaided eye, appeared through a field glass as globes of nebulous light, dense at the core and fading gently toward the borders. Viewed through the 13-inch Boyden telescope, such clusters resolved into swarms of stellar bees. The abundance of individual components challenged Bailey to take a census of their populations. He began by capturing a single cluster in a two-hour exposure made the night of May 19, 1893. On a separate glass plate he ruled lines to produce a grid of four hundred tiny boxes. Laying the grid over the glass negative, and placing the pair under a microscope, he counted the stars in each compartment. “The cross-hairs of the eyepiece divided each square into four sub-squares,” he reported to Astronomy and Astro-Physics in June, “which served to prevent confusion in counting.” Even so, he asked Ruth Bailey to count, too, for confirmation. When he saw that his wife’s tally somewhat exceeded his own, he averaged their results to arrive at a total of at least 6,389 stars in the cluster called Omega Centauri. “There can be no doubt, however,” he added, given the difficulty of assessing the closely packed center, “that the whole number of stars comprising this splendid cluster is very much greater.” Then he proceeded to gauge the brightness of the individual cluster members, one row at a time, by comparing each star to its neighbors, in sequence—8.7, 9.5, 8.8, 8.5, 9, 8.8, 9.2, and so on.
Bailey thought he might devote his life to the study of clusters, but not at the expense of his regular duties. He kept up the steady flow of chart plates and spectra plates. He outfitted a new meteorology station—the world’s highest—at the summit of El Misti with the help of his older brother, Hinman. Their younger brother, Marshall, disaffected by the exhausting work of the initial Peruvian expedition, had declined a second stint at Arequipa and enrolled instead in the College of Physicians and Surgeons in Baltimore.
The globular clusters soon proved themselves fertile hunting grounds for variable stars. Mrs. Fleming picked out the first one in Omega Centauri in August, and Pickering found another a few days later. As these discoveries multiplied, a malcontent from within the Harvard ranks undermined their validity by attacking the observatory’s procedures.
Seth Carlo Chandler, a variable star aficionado, had served under Pickering from 1881 to 1886 as a research associate and calculator of comet orbits. After leaving his post, he continued his affiliation with the observatory by helping to issue telegraph alerts of comet sightings and other time-sensitive information to the global astronomy community. In 1888 he released a catalogue of variable stars, complete with his own detailed numerical analyses
